The rising problem of antibiotic resistance has led to fears that medicine will return to the situation of a century ago when extensive wounds and surgery often led to death due to uncontrollable infection. These fears have in turn spurred a major research effort to find alternative antimicrobial approaches which, it is hypothesized, will kill resistant micro-organisms while being unlikely to cause resistance to develop to themselves. At the present time many international research efforts to discovery new antimicrobials are underway. Recently, the emphasis is on how to take precautions against creating, and if possible eliminate multidrug resistance in concert with exploring new methods to kill pathogenic microorganisms. Karen et al. in “Tackling antibiotic resistance,” Bush K, Nat Rev Microbiol. 2011 Nov. 2; 9(12):894-6, recently pointed out that the investigation of novel non-antibiotic approaches, which can prevent and protect against infectious diseases should be encouraged, and should be looked upon as a high-priority for research and development projects.
The best known source of sterilization is UV-C radiation (wavelength: 200-280 nm). Among this wavelength range, the optimum range of 250-270 nm has the optimum potential ability to inactive microorganisms because it is strongly and mainly absorbed by nucleic acids of microbial cells and, therefore is the most lethal range of wavelengths.
The bactericidal mechanism of UV-C is to cause damage to their RNA and DNA, which often leads to the formation of dimers between pyrimidine residues in the nucleic acid strands. The consequence of this modification is that the production of cyclobutane pyrimidine dimers (CPDs) causes deformation of the DNA molecule, which might cause defects in cell replication and lead to cell death afterwards.
It is well known that prolonged and repeated exposure to UV irradiation can damage host cells and be particularly hazardous to human skin. As to long-term UVC irradiation of human skin, it is also known to have potential carcinogenicity. When UVC irradiation is applied to treat localized infections, one must consider the possible side-effects of UVC delivered at effective antimicrobial fluences on normal mammalian cells and tissue. The safety issue of UVC germicidal treatment requires that the pathogenic microbe is selectively eradicated while the normal tissue cells are spared.
It has been found that no significant adverse effects were induced in human primary corneal epithelial cells when the cells were exposed to 1.93 mJ/cm2 UVC (265 nm), which induced 100% inhibition of growth of all the bacterial species cultured on agar plates. UVC has been used to reduce pathogen contamination of platelet concentrates. The results showed UVC inactivated more than 4 log 10 Gram-positive S. aureus, Bacillus cereus and S. epidermidis, and Gram-negative E. coli, P. aeruginosa and Klebsiella pneumoniae. 
Most of the experimental results mentioned above suggest that UVC at appropriate fluences does not cause significant damages to host cells and tissues. However, UVC irradiation still has potential to induce nonspecific damage. Studies demonstrated that the DNA of mammalian cells could indeed be damaged by UVC at its effective antimicrobial fluences. Fortunately however, at the same time, the DNA repairing enzymes of the host cells could rapidly repair the damaged DNA. In addition, to minimize the UVC-induced non-specific damage, the intact skin around the area to be treated could be shielded from UVC illumination. On the other hand, application of UVC is limited in some special locations due to its detrimental effects such as infections of the eyes.
A study presented by Taylor et al., reported that the mean bacterial CFU in joint arthroplasty surgical wounds was reduced by 87% with 0.1 mW/cm2 (P<0.001) and 92% with 0.3 mW/cm2 (P<0.001) of UVC. Thai et al. used UVC irradiation to treat cutaneous ulcers infected with MRSA. In all three patients, UVC treatment reduced the bacterial burden in wounds and promoted wound healing. Two patients had complete wound closure following 1 week of UVC treatment. Another trial was carried out by the same investigators in 22 patients with chronic ulcers manifesting at least two signs of infection and critically colonized with bacteria. The patients received a single UVC treatment and demonstrated significantly reductions of the bacterial burden. In a study, thirty patients with mild-to-moderate toenail onychomycosis were used to treat with UVC. Improvement by at least 1 measurement point was achieved in 60% of patient at 16-week follow-up compared with baseline. There were some unusual and slight side effects such as temporary mild eythema of the treated toe. In addition to the inactivation of microbial cells in the cutaneous wound, UVC exposure is beneficial for wound healing by promoting the expression of basic fibroblast growth factor (bFGF) and transforming growth factor, although the exact mechanisms of UVC for wound healing is still unclear. Others have investigated the prophylactic efficacies of UVC irradiation in 18 cases of catheter exit-site infections. Although five cases remained unchanged, ten cases (55%) became culture negative and a further three cases showed a microbial decrease.
In summary, it has been known during the past one-hundred years that UVC irradiation is highly bactericidal; however, using UVC illumination for the prophylaxis and treatment of localized infections is still at very early stages of development. Most of the studies are limited to in vitro and ex vivo levels, while in vivo animal studies and clinical studies are much rarer. A major advantage of using UVC over antibiotics is that UVC can eradicate resistant and pathogenic microorganisms much more rapidly without any systemic side-effects. UVC may also be much more cost effective than the commonly used antibiotics.
What is needed is a system that will expose a locale of a human (or animal) to UVC and ozone to reduce or eliminate pathogens.